A(b-3c)-2(b+3с)
cпособ группировки
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Решаем уравнением
Х- скорость первого
Х+25-скорость второго
(Х+Х+25)*2=350
4Х+50=350
4Х=300
Х=300/4
Х=75
Х+25=100
Lim[(6*4^n+1-3*2^(n+1))/(3*2^2n+1)]=lim](6*4^n-6*4^n-2*2^n)/(3*2^n+1)]=
=lim[(-2*2^n)/(3*2^n+1)]=lim[2^n*(-2)/(2^n*(3+1/2^n))]=
=lim[-2/(3+1/2^n)]=-2/3
Ответ А